One example of a known internal combustion engine is contained in U.S. Pat. No. 5,743,219, incorporated by reference herein. At the heart of this engine is a plurality of cylinders that house pistons. The cylinders are in communication with air and fuel intakes. Incoming air and fuel is compressed and ignited in a reciprocal fashion that drives the pistons which, through known means, drive the motorcycle's wheel. The timing and amount of fuel and air entering the cylinder is typically controlled by valves. Similarly, valves control the release of exhaust gases after combustion. Operation of these valves may be controlled by cams that selectively open and close the valves during the cam's rotation. The cam profile determines the period and amount of valve displacement. Often the cam is placed in operative contact with a rocker arm that acts as an intermediary between the cam and valve. At times, a single cam uses a rocker arm to actuate more than one valve. The rocker arm is pivotally mounted above and in contact with one or more valves, and a cam rides along the opposite surface of the rocker arm depressing and releasing the rocker arm as it rotates. In turn, the valves are depressed and released by the rocker arm. Typically, rocker arms are spring mounted to maintain contact with the cam.
Known rocker arms for motorcycles employ a raised striking surface made of polished chrome at the point of contact between the cam and rocker arm. A cam located above the striking surface engages the polished chrome striking surface. As the cam rotates, its surface slides across the string surface, creating significant frictional forces. The surface contact between the cam and rocker arm abrades these surfaces and produces heat, shortening the operative life of each component. The heat causes the component materials to expand, increasing the functional forces and wear. Due to the cyclic motion of the cam, the amount of contact increases with engine speed. At elevated engine speeds, the wearing of the polished chrome surface forms minute beads or balls of chrome material on the surface of the striking plate. These beads dramatically abrade the cam and striking plate surfaces in a short period of time. This abrasion significantly shortens cam and rocker arm life.
In further detriment, the frictional forces between the plate and cam sap the engine's usable horsepower. The force needed to rotate the cam is related to the frictional forces because these must be overcome to rotate the cam. Since more horsepower is committed to rotating the cam, less horsepower is available to drive the motorcycle and, thus, the motorcycle suffers reduced performance.
Therefore, there is a need for a rocker arm that improves cam and rocker arm life and reduces the frictional forces between the cam and rocker arm.